Preheat the oven to 350 degrees F. Line several baking sheets with parchment paper. Whisk the flour, salt, and baking soda together in a medium bowl, and set aside. In a large bowl, cream the butter and sugars with a hand held electric mixer, until light and fluffy. Beat in the egg and then the vanilla. Gradually add the dry ingredients to the creamed mixture. Stir in the chopped chocolate. To form the cookies, scoop level teaspoons of the dough and roll by hand into balls. Place the balls about 2 inches apart on the baking sheets. Flatten the dough slightly with your fingertips. Bake until light brown, about 12 minutes. (If baking 2 sheets at a time, rotate the pans halfway through baking.) Transfer cookies to a rack to cool.